Nanomechanical, structural, and transport properties of Bi₃Se₂Te thin films

New ternary phase of Bi₃Se₂Te thin films were successfully grown through pulsed laser deposition with a single Bi₂Se₂Te crystal as the target. Bi-rich and Se- and Te-deficient compositions deposited at a substrate temperature (T_s) of 250°C and helium gas pressures (P_He) ranging from 2.0 × 10^-5 to 6.5 × 10^-1 Torr aided the formation of the dominant Bi-rich phase: Bi₃Se₂Te. The films were grown epitaxially on Al₂O₃ (001) substrates with Bi₃Se₂Te [001]//Al₂O₃ [001] and Bi₃Se₂Te [110]//Al₂O₃ [210]. An increase in P_He remarkably enhanced the hardness and Young's modulus of the films, primarily because of the decrease in nanograin size, following the Hall-Petch relationship. Moreover, the Bi₃Se₂Te films present linear magnetoresistance under a high perpendicular magnetic field (B ≥ 4 T) and two-dimensional weak antilocalization effect under a low B (±1 T) which may be attributed to topological insulator surface state (TSS). Clearly, further theoretical calculations and experiments are needed to confirm the suggested interpretation.